Authentication system

ABSTRACT

The present invention enables the degree of freedom in communication to be enhanced. According to the present invention, in an authentication system  1 , during a walking motion of a user which is essentially required for the user to pass through an entrance/exit passage portion  4  (FIG.  6 ), tissue information D 5  and walking information D 7  as living organism identification information, a pattern specific to a user, is detected from an detection electrode  52  via an FET  11 , based on a walking quasi-electrostatic field HSE formed in the neighborhood of the user. Thereby, information with high identifiability specific to the user can be obtained without controlling movements of the user and without performing special processing such as encryption. Thus, the degree of freedom in communication can be enhanced.

TECHNICAL FIELD

The present invention relates to a communication system and ispreferably applicable to a communication system for sending andreceiving information via an electric field, for example.

BACKGROUND ART

Conventionally, communication systems have been adapted to send andreceive information using a radiation field (radio waves), for example,between mobile telephones, and send and receive information viaelectromagnetic induction, for example, between the coil in a datareader/writer provided on a ticket checking and collecting machine at astation and the coil in an IC card.

Recently, there have been proposed communication systems which areprovided with a human-body-side communication device fitted in contactwith the skin of a human body and an equipment-side communication devicein the neighborhood of the user as shown in Table 1 below. In thesecommunication systems, an alternating voltage is applied to the humanbody via the electrode of the human-body-side communication device, andas a result, there is caused an electrostatic induction phenomenon atthe electrode of the equipment-side communication device by the actionof a capacitor using a human body intervening between the electrodes ofthe communication device on the human body side and the communicationdevice on the equipment side as a medium. Using the electrostaticinduction phenomenon, information is sent and received (see Non-patentdocument 1, for example).

In addition to the communication systems shown in Table 1, there havebeen proposed a lot of communication systems adapted to send and receiveinformation utilizing the electrostatic induction phenomenon caused at areceiving electrode by the action of a capacitor using a human bodyintervening between sending and receiving electrodes as a medium (seePatent documents 1 to 9 and Non-patent documents 2 to 5).

[Patent document 1] National Publication of International PatentApplication No. 11-509380

[Patent document 2] Patent No. 3074644

[Patent document 3] Japanese Patent Laid-Open No. 10-228524

[Patent document 4] Japanese Patent Laid-Open No. 10-229357

[Patent document 5] Japanese Patent Laid-Open No. 2001-308803

[Patent document 6] Japanese Patent Laid-Open No. 2000-224083

[Patent document 7] Japanese Patent Laid-Open No. 2001-223649

[Patent document 8] Japanese Patent Laid-Open No. 2001-308803

[Patent document 9] Japanese Patent Laid-Open No. 2002-9710

[Non-patent document 1] Internet<URL:http://www.mew.co.jp/press/0103/0103-7.htm> (retrieved on Jan. 20,2003)

[Non-patent document 2] “Development of Information Communication Devicewith Human Body Used as Transmission Line” by Keisuke Hachisuka, AnriNakata, Kenji Shiba, Ken Sasaki, Hiroshi Hosaka and Kiyoshi Itao (TokyoUniversity); Mar. 1, 2002 (Collected Papers for Academic Lectures onMicromechatronics, Vol., 2002, Spring, pp. 27-28)

[Non-patent document 3] “Development of Communication System withinOrganism” by Anri Nakata; Keisuke Hachisuka, Kenji Shiba, Ken Sasaki,Hiroshi Hosaka and Kiyoshi Itao (Tokyo University); 2002 (CollectedPapers for Academic Lectures for Japan Society of Precision EngineeringConference, Spring, p. 640)

[Non-patent document 4] “Review on Modeling of Communication SystemUtilizing Human Body as Transmission Line” by Katsuyuki Fujii (ChibaUniversity), Koichi Date (Chiba University), Shigeru Tajima (SonyComputer Science Laboratories, Inc.); Mar. 1, 2002 (Technical Reports byThe Institute of Image Information and Television Engineers Vol. 26, No.20, pp. 13-18)

[Non-patent document 5] “Development of Information Communication Devicewith Human Body Used as Transmission Line” by Keisuke Hachisuka, AnriNakata, Kento Takeda, Ken Sasaki, Hiroshi Hosaka, Kiyoshi Itao (GraduateSchool of Science of New Region Creation, Tokyo University) and KenjiShiba (Science and Engineering Course, Tokyo University of Science);Mar. 18, 2002 (Micromechatronics Vol. 46; No. 2; pp. 53-64)

In these communication systems with such a configuration, since theaction of a capacitor using a human body intervening between sending andreceiving electrodes as a medium is the premise of physical action, thecommunication strength in communication between the electrodes dependson the area of the electrodes.

Furthermore, since the action of a capacitor using a human bodyintervening between sending and receiving electrodes as a medium is thepremise of physical action, it is physically impossible, when thesending electrode is fitted to the human's right wrist, for example, tocommunicate in directions other than the direction from the human'sright wrist to the fingertip. When the sending electrode is fitted nearthe human's chest, communication in directions other than the forwarddirection from the human's chest is physically impossible.

As described above, in communication systems, since the action of acapacitor using a human body intervening between sending and receivingelectrodes as a medium is the premise of physical action, there havebeen a problem that the communication direction is restricted by theposition of the electrode fitted to a human body as well as a problemthat the degree of freedom in communication is low because thecommunication strength depends on the electrode area.

DISCLOSURE OF THE INVENTION

The present invention has been made in consideration of the aboveproblems and proposes a communication system, a communication method anda communication device capable of enhancing the degree of freedom incommunication.

According to the present invention, for the purpose of solving the aboveproblems, in an authentication system comprising a sending device and areceiving device for sending and receiving information via aquasi-electrostatic field, the sending device is adapted to detectorganism information specific to a human body, generate aquasi-electrostatic field modulated according to the organisminformation and thereby electrify the human body, while the receivingdevice is adapted to demodulate the organism information based on changein the electrification condition of the human body and identify thehuman body based on the organism information.

Consequently, the authentication system is able to realize sending andreceiving of information without directional restrictions in theneighborhood of the user, with confidentiality secured, and withoutforcing the user to perform a predetermined movement, and it is alsoable to identify even the relation between the device and the human bodybased on information specific to the human body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram provided to explain a polar coordinatesystem;

FIG. 2 is a graph showing relative strength change (1) of each electricfield relative to the distance;

FIG. 3 is a graph showing relative strength change (2) of each electricfield relative to the distance;

FIG. 4 is a graph showing the relation between the wavelength and thedistance;

FIG. 5 is a schematic diagram provided to explain the tissue of a humanbody;

FIG. 6 is a schematic diagram showing the entire configuration of anauthentication system to which the present invention is applied;

FIG. 7 is a schematic block diagram showing the configuration of a carddevice;

FIG. 8 is a schematic diagram showing the configuration of amicroelectrode;

FIG. 9 is a block diagram showing the configuration of a waveformprocessing portion;

FIG. 10 is a schematic diagram provided to explain a walking waveform;

FIG. 11 is a schematic diagram provided to explain cutout and divisionof a waveform;

FIG. 12 is a flowchart showing a procedure for a sending process;

FIG. 13 is a flowchart showing a procedure for a masking timedetermination process;

FIG. 14 is a flowchart showing a procedure for a walking informationgeneration process;

FIG. 15 is a schematic block diagram showing the configuration of anauthentication device;

FIG. 16 is a graph provided to explain integral values for subdividedsections;

FIG. 17 is a flowchart showing a procedure for an authenticationprocess;

FIG. 18 is a flowchart showing a procedure for a walking waveformchecking process;

FIG. 19 is a schematic diagram provided to explain an example ofcalculating the Mahalanobis' distance;

FIG. 20 is a schematic diagram provided to explain the floor surface ofthe authentication device;

FIG. 21 is a schematic diagram showing the equipotential surface of aquasi-electrostatic field to be formed when a human body is caused toact as an ideal dipole antenna;

FIG. 22 is a schematic diagram showing the equipotential surface of aquasi-electrostatic field performed according to this embodiment;

FIG. 23 is a schematic diagram provided to explain prevention ofelectrical leakage; and

FIG. 24 is a schematic diagram showing the configuration of a noiseabsorption/grounding line.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is now described in detail with reference to thedrawings.

(1) Summary of the Invention

According to the invention, information is sent and received using anelectric field. The summary of the present invention is now described interms of the relation with the electric field.

(1-1) Electric Field

Generally, when current flows through an electric dipole (dipoleantenna), the electric field E generated according to the distance rfrom the antenna can be represented in a simplified formula as shownbelow: $\begin{matrix}{E_{0} = {A\left( {\frac{1}{r^{3}} + \frac{jk}{r^{2}} + \frac{k^{2}}{r^{1}}} \right)}} & (1)\end{matrix}$where j is an imaginary unit, A is a constant, and k is the number ofwaves.

As shown in the above formula (1), the electric field E can be roughlyseparated into a component which is in inverse proportion to thedistance r raised to the third power (hereinafter, this component isreferred to as a quasi-electrostatic field), a component which is ininverse proportion to the distance r raised to the second power(hereinafter, this component is referred to as an induction field) and acomponent which is linearly in inverse proportion to the distance r(hereinafter, this component is referred to as a radiation field).

The radiation field is a component excellent in propagation capability,which does not rapidly attenuate even when the distance r is long, sinceit is only linearly in inverse proportion to the distance r, andtherefore, it has been used as a common information transmission mediumin the art of information communication.

Though the induction field is a component with little transmissioncapability, which attenuates in inverse proportion to the distance rraised to the second power as the distance r lengthens, it has recentlybeen used as an information transmission medium in a part of the art ofinformation of communication.

The quasi-electrostatic field is a component which rapidly attenuates ininverse proportion to the distance r raised to the third power andtherefore does not a transmission capability and which appears in closeproximity to an oscillation source only as oscillation. Therefore, ithas not been utilized in the art of information communication where theradiation field and the induction field are premises.

The present invention is adapted to send and receive information withina neighbor communication range, with a neighbor communication(hereinafter referred to as near field communication) approach using aquasi-electrostatic field among electric fields.

(1-2) Quasi-Electrostatic Field

The quasi-electrostatic field is now described in more detail. First,the electric field E shown in the above formula (1) is represented as anelectric field at a position P (r, θ, φ) at a predetermined distancefrom the origin as described in FIG. 1.

In this case, if it is assumed that a charge q and a charge −q existseparated by a distance δ and the charge q changes to “Qcosωt” at a timet, then the electric fields Er, Eθ and Eφ at the position P (r, θ, φ)can be represented as the following formulas, respectively, with theposition of the charge q as the origin: $\begin{matrix}{{E_{1} = {\frac{Q\quad\cos\quad\omega\quad t\quad\sigma\quad\cos\quad\theta}{2\pi\quad ɛ\quad r^{3}}\left( {1 + {jkr}} \right){\exp\left( {- {jkr}} \right)}}}{E_{\theta} = {\frac{Q\quad\cos\quad\omega\quad t\quad\sigma\quad\sin\quad\theta}{4\pi\quad ɛ\quad r^{3}}\left( {1 + {jkr} + ({jkr})^{2}} \right){\exp\left( {- {jkr}} \right)}}}{E_{\phi} = 0}} & (2)\end{matrix}$

In the formulas (2), the electric field Eφ is “zero”, and this meansthat there is not generated any electric field in the direction from theposition P (FIG. 1).

If the component which is linearly in inverse proportion to the distancer (that is, the radiation field) is separated from the electric fieldsEr and Eθ represented in the formulas (2), then the radiation field E1 rand E1θ at the position P (r, θ, φ) are represented as the followingformulas: $\begin{matrix}{{E_{1r} = 0}{E_{1\theta} = {\frac{Q\quad\cos\quad\omega\quad t\quad\sigma\quad\sin\quad\theta}{4\pi\quad ɛ\quad r}({jk})^{2}{\exp\left( {- {jkr}} \right)}}}} & (3)\end{matrix}$If the component which is in inverse proportion to the distance r raisedto the second power (that is, the induction field) is separated from theelectric fields Er and Eθ represented in the formulas (2), then theinduction fields E2 r and E2θ at the position P (r, θ, φ) arerepresented as the following formulas: $\begin{matrix}{{E_{2\quad r} = {\frac{Q\quad\cos\quad\omega\quad t\quad\sigma\quad\cos\quad\theta}{2\pi\quad ɛ\quad r^{2}}{{jk} \cdot {\exp\left( {- {jkr}} \right)}}}}{E_{2\quad\theta} = {\frac{Q\quad\cos\quad\omega\quad t\quad\sigma\quad\sin\quad\theta}{4\pi\quad ɛ\quad r^{2}}{{jk} \cdot {\exp\left( {- {jkr}} \right)}}}}} & (4)\end{matrix}$Furthermore, if the component which is in inverse proportion to thedistance r raised to the third power (that is, the quasi-electrostaticfield) is separated from the electric fields Er and Eθ represented inthe formulas (2), then the quasi-electrostatic fields E3 r and E3θ atthe position P (r, θ, φ) are represented as the following formulas:$\begin{matrix}{{E_{3r} = \frac{Q\quad\cos\quad\omega\quad t\quad\sigma\quad\cos\quad\theta}{2\pi\quad ɛ\quad r^{3}}}{E_{3\quad\theta} = \frac{Q\quad\cos\quad\omega\quad t\quad\sigma\quad\sin\quad\theta}{4\pi\quad ɛ\quad r^{3}}}} & (5)\end{matrix}$

In the formulas (3), only the radiation field E1 r is “zero”, and thismeans that the tangent direction components at the position P (FIG. 1)is zero.

Now, in order to show the component's electric field strength of each ofthe radiation field, the induction field and the quasi-electrostaticfield at a distance r, the radiation field E1θ, the induction field E2θand the quasi-electrostatic field E3θ in the formulas (3) to (5) are nowdescribed in more detail.

The number of waves k [m⁻¹] is in the relation shown as the followingformula, where the angular frequency is denoted by ω and the lightvelocity is denoted by c: $\begin{matrix}{k = \frac{\omega}{c}} & (6)\end{matrix}$If the number of waves k is substituted into the formula (6), the“j·exp(−jkr)” is removed since it is beyond the discussion here, and the“cosωt” is assumed to be one (1) since the maximum change with timebetween the charge q and the charge −q is to be considered, then thefollowing formulas are obtained: $\begin{matrix}{{{Radiation}\quad{field}}\quad{E_{1\quad\theta} = {\frac{Q\quad\sigma\quad\sin\quad\theta}{4\pi\quad ɛ\quad r^{3}}\left( {\frac{\omega}{c}r} \right)^{2}}}{{Induction}\quad{field}}\quad{E_{2\quad\theta} = {\frac{Q\quad\sigma\quad\sin\quad\theta}{4\pi\quad ɛ\quad r^{3}}\frac{\omega}{c}r}}{{Quasi} - {{electrostatic}\quad{field}}}\quad{E_{3\theta} = \frac{Q\quad\sigma\quad\sin\quad\theta}{4\pi\quad ɛ\quad r^{3}}}} & (7)\end{matrix}$If the formulas (7) are rearranged by substituting the distance δ, thecharge q (=Q) and the θ with one (1), 0.001 [C] and π/2, respectively,then the following formulas are obtained: $\begin{matrix}{{{Radiation}\quad{field}}\quad{E_{1\quad\theta} = {\frac{0.001}{4\pi\quad ɛ_{0}r}\left( \frac{\omega}{c} \right)^{2}}}{{Induction}\quad{field}}\quad{E_{2\quad\theta} = {\frac{0.001}{4\pi\quad ɛ_{0}r^{2}}\frac{\omega}{c}}}{{Quasi} - {{electrostatic}\quad{field}}}\quad{E_{3\theta} = \frac{0.001}{4\pi\quad ɛ_{0}r^{3}}}} & (8)\end{matrix}$

FIGS. 2 and 3 shows the results obtained by qualitatively plotting thecomponent's electric field strengths of the radiation field E1θ, theinduction field E2θ and the quasi-electrostatic field E3θ based on theformulas (8).

However, in FIGS. 2 and 3, the component's electric field strengths at afrequency of 1 [MHz] are shown, and in FIG. 3, a relation betweencomponent's distance and electric field strength shown in FIG. 2 isshown by a graph with a measure of logarithm.

Especially apparent from FIG. 3, the component electric field strengthsof the radiation field E1θ, the induction field E2θ and thequasi-electrostatic field E3θ are equal at a certain distance r(hereinafter referred to as a boundary point), and the radiation fieldE1θ is dominant in the distance from the boundary point. On thecontrary, in the neighbor before the boundary point, thequasi-electrostatic field E3θ is dominant.

At the boundary point, the following formula is established according tothe above formulas (8): $\begin{matrix}{{\frac{\omega}{c} \cdot r} = 1} & (9)\end{matrix}$The light velocity c is in the relation shown by the following formula,where the wavelength is denoted by λ and the frequency is denoted by f:c=λ·f  (1)The angular frequency ω is in the relation shown by the followingformula:ω=2πf  (11)Then, by substituting the formula (10) and the formula (11) into theformula (9) and rearranging the formula (9), the following formula isobtained: $\begin{matrix}{r = \frac{\lambda}{2\pi}} & (12)\end{matrix}$

According to the formula (12), the distance r from the origin to theboundary point varies according to the wavelength λ. As shown in FIG. 4,the longer the wavelength λ is, the wider the range (the distance r fromthe origin to the boundary point) where the quasi-electrostatic fieldE3θ is dominant.

To sum up the above description, the quasi-electrostatic field E3θ isdominant within the range where the distance r from the origin is“r<λ/2π”, if the relative permittivity of the air ε is assumed to be 1and the wavelength in the air is assumed to be λ.

In the present invention, by selecting the range satisfying the formula(12) when sending and receiving information with the near fieldcommunication approach, the information is sent and received in thespace where the quasi-electrostatic field E3θ is dominant.

(1-3) A Quasi-Electrostatic Field and a Human Body

Though it is necessary to apply current to a human body to cause thehuman body to generate a radiation field or an induction field, it isphysically difficult to efficiently apply current to the human bodybecause the impedance of a human body is very high. It is alsophysiologically undesirable to apply current to a human body. As forstatic electricity, however, the situation is completely different.

That is, a human body is very often electrified as suggested by theempirical fact that static electricity is felt in our everyday life. Asit is known that a quasi-electrostatic field is generated byelectrification of the surface of a human body in response to themovement of the human body, it is not necessary to apply electricity toa human body to cause the human body to generate a quasi-electrostaticfield but it is only necessary to electrify the human body.

That is, a human body is electrified by extremely little movement ofcharge (current); the electrification change is instantaneouslyconducted around the surface of the human body; and then anequipotential surface of a quasi-electrostatic field is formedsubstantially isotropically from the periphery. Furthermore, within therange satisfying the above formula (12) where the quasi-electrostaticfield is dominant, the radiation field and the induction field does nothave much influence. Consequently, the human body functions efficientlyas an antenna. This has already been confirmed from the results of theexperiments by the applicant.

As a near field communication technology, the present information isadapted to modulate a quasi-electrostatic field which is isotropicallyformed in the neighborhood of a human body by electrifying the humanbody according to particular information, and as a result, form aquasi-electrostatic field having information in the neighborhood of thehuman body, through which the information is sent and received.

(1-4) A Quasi-Electrostatic Field and a Walking Motion of a Human Body

As already stated, the surface of a human body is electrified inresponse to a movement of the human body. Description will be now madeon the relation between walking, one of major movements of a human body,and electrification in more detail. Such relation is already disclosedin Japanese Patent Application No. 2002-314920 by the applicant.

That is, as for displacement of the strength of a quasi-electrostaticfield formed as the surface of a human body is electrified by the humanbody's walking motion (hereinafter, it is referred to as a walkingquasi-electrostatic field), not only movement of a charge between thepassage surface and the plantar surface but also change in theexfoliation area (or the contact area) of the plantar surface relativeto the passage surface and change in the distance between the passagesurface and the plantar surface are closely involved.

In other words, the electrification change on the surface of a humanbody caused by a walking motion of the human body reflects a patternspecific to the individual, which is generated by change in theelectrostatic capacity and charge between the feet and the passagesurface according to the trajectory of the feet made by the walkingmotion and in which mutual movements of the right and left feet arecombined. Thus, the pattern of electrification change on the surface ofa human body which is generated by a walking motion of the human bodyreflects the characteristics of the organism (human body), and thereforehigh accuracy of authentication can be expected therefrom.

Accordingly, the present invention is adapted to generate organismidentification information indicating a walking pattern specific to ahuman body, based on the pattern of electrification change on thesurface of the human body generated by a walking motion of the humanbody, and use the organism identification information to perform apredetermined authentication process.

At the instant when the tiptoe of the right foot (left foot) hascompletely left the ground, the left foot (right foot) is completely incontact with the passage surface, irrespective of difference in thewalking condition, according to walking characteristics.

Accordingly, in such a condition, mutual electrification action(interference action) between the right and left feet does not occur,and in displacement of strength of the walking quasi-electrostatic fieldin this condition, the highest peak amplitude appears specificallywithin the band of 8 Hz±2 Hz.

As for details of the amplitude peak which appears within the band of 8Hz±2 Hz (hereinafter referred to as the 8 Hz peak), see Japanese PatentApplication No. 2002-314920 (paragraph No. [0024] on p. 5 to paragraphNo. [0056] on p. 12) already disclosed by the applicant. The walkingmotion described in the invention means a movement of walking on a flatpassage surface without being especially conscious of the speed.

As described above, the 8 Hz peak with the highest strength appears in awalking quasi-electrostatic field formed in the neighborhood of a humanbody when a walking motion is performed, therefore, if attempting toelectrify a human body to form a quasi-electrostatic field havinginformation in the neighborhood of a the human body, for the purpose ofperforming near field communication, the information may be destroyed bythe 8 Hz peak.

Therefore, the present invention is adapted to avoid destruction ofinformation by the 8 Hz peak by electrifying a human body according toinformation while avoiding the timing when such 8 Hz peak appears.

(1-5) A Quasi-Electrostatic Field and the Tissue Structure of a HumanBody

The subepidermal tissue structure of a human body comprises epidermallayers SL and dermal layers BL constituted of epidermoid cells, as shownin FIG. 5, and various proteins are contained in the dermal layers BL,such as collagen classified as structural protein and hemoglobinclassified as transport protein. It has been already confirmed by theapplicant that the pattern of the subepidermal tissue structure isinformation specific to an individual.

As an approach for detecting the pattern of the subepidermal tissuestructure, approaches described are conceivable, for example. In a firstapproach, the potential of a human body with multiple planarmicroelectrodes attached to the epidermal surface thereof, that iselectrified when it enters a quasi-electrostatic field, is detected byeach of the microelectrodes as a relative potential difference.

In a second approach, which utilizes the fact that a human body iselectrified by a walking motion thereof as described above, thepotential of a human body with multiple planar microelectrodes attachedto the epidermal surface thereof, that is electrified when it walks, isdetected by each the microelectrodes as a relative potential difference.

In both of the two approaches described above, electrostatic capacitydifference between the structure under each microelectrode and themicroelectrode is detected. This means that the tissue structure undereach microelectrode, that is, the pattern of tissue to be informationfor identifying an individual is detected. In the two approaches,high-frequency signals for detection are not directly applied to theskin externally, and therefore, it is considered that physiologicalburden is not imposed on the human body when detection is performed.

For example, if one microelectrode arranged on the surface of a humanbody is represented by EN(i), the distance to the deepest layer of thedermal layers BL under the microelectrode EN(i) is represented by md(i),and the relative permittivity is represented by ε, and the permittivityof vacuum electric constant is represented by ε0, then the electrostaticcapacity C(i) between the microelectrode EN(i) and the deepest layer ofthe dermal layers BL under the microelectrode EN(i) with the distancemd(i) therebetween is represented by the following formula:$\begin{matrix}{{C(i)} = {ɛ\quad ɛ_{0}\frac{S}{{md}(i)}}} & (13)\end{matrix}$and the potential V(i) detected by the microelectrode EN(i) when thehuman body is electrified with a charge Q is represented by thefollowing formula: $\begin{matrix}{{V(i)} = {Q \cdot \frac{{md}(i)}{{ɛɛ}_{0}S}}} & (14)\end{matrix}$Actually, the detected potential is influenced not only by the distancemd(i) from the microelectrode EN(i) to the deepest layer of the dermallayers BL but also by the presence of cutaneous veins and the like.

Therefore, it is difficult to accurately determine the distance md(i)with limitation only to blood vessels, for example, included in thedermal layers BL, and the presence of subepidermal blood vessels is alsoreflected in the measured value. It is known that subepidermal tissuestructure indicates characteristics specific to an individual and ispermanent in relation to fingerprints, for example, and the same is trueon the vein pattern. Accordingly, the potential difference pattern foreach microelectrode reflects the characteristics of the living tissueincluding the subepidermal tissue and veins below the electrode, andtherefore high accuracy of authentication can be expected.

Accordingly, the present invention is adapted to generate livingorganism identifying information indicating a tissue pattern specific toa human body based on a potential difference pattern characterizing theliving tissue, and performs a predetermined authentication process usingthe living organism identifying information.

As described above, the present invention utilizes the nature of aquasi-electrostatic field and the nature of a human body. To sum up thepresent invention, within a range where a quasi-electrostatic field isdominant, the sending side generates living organism identifyinginformation indicating a walking pattern obtained based on theelectrification change on the surface of a human body, which is causedby a walking motion of the human body, and a living tissue pattern; thenelectrifies the human body to cause the human body to act as an antennafor the purpose of near field communication while avoiding the timingwhen the 8 Hz peak appears; and, as a result, forms aquasi-electrostatic field having living organism identifying informationin the neighborhood of the human body.

Meanwhile, the receiving side, after detecting the living organismidentifying information via the quasi-electrostatic field formed in theneighborhood of the human body, performs a predetermined authenticationprocess using registrant information registered in advance. Oneembodiment to which the present invention is applied will be nowdescribed below.

(2) One Embodiment of the Present Invention

(2-1) Entire Configuration of an Authentication System

In FIG. 6, reference numeral 1 denotes the entire configuration of anauthentication system to which the present invention is applied.

The authentication system comprises an authentication device 2 provided,for example, at the entrance of a company, and a mobile device(hereinafter referred to as a card device) 3 attachably and detachablyprovided on a predetermined position of the arm of a human body(hereinafter referred to as a user) that utilizes the company.

The authentication device 2 comprises an entrance/exit passage portion 4provided for entrance and exit, and an exit door 5 openably and closablyprovided on the exit side of the entrance/exit passage portion 4, and isadapted to perform near field communication with the card device 3provided on the user who is passing through the entrance/exit passageportion 4 and open the exit door 5 which is closed, as necessary.

(2-2) Configuration of a Card Device

As shown in FIG. 7, the card device 3 comprises an electric fielddetection portion 10, a sending portion 20 and an electrificationinduction portion 30.

The electric field detection portion 10 has a field effect transistor(hereinafter referred to as an FET) 11, and the gate of the FET 11 isconnected to the user's epidermis OS, which is a detection target, viaan detection electrode 12 and a dielectric 13 sequentially. The sourceand the drain of the FET 11 are connected to an amplifier 14.

The electric field detection portion 10 is adapted to detect strengthchange of a walking quasi-electrostatic field HSE (FIG. 7) formed in theneighborhood of a user, which is caused by electrification of thesurface of the user coming near to the entrance/exit passage portion 4,via the dielectric 13 and the detection electrode 12 sequentially, andsend it to the sending portion 20 as an amplified walkingelectrification change signal S1 via the amplifier 14.

In this case, since strength change of the walking quasi-electrostaticfield HSE formed in response to a walking motion of a user appears at aninfrasonic frequency band, the electric field detection portion 10 isable to accurately detect the strength change substantially withoutbeing influenced by noises such as hum noises.

The electric field detection portion 10 contacts the dielectric 13directly with the user's epidermis OS and thereby can detect thestrength change of the walking quasi-electrostatic field HSE with highsensitivity. Furthermore, by forming the dielectric 13 with soft vinylchloride with a high permittivity, for example, the strength change canbe detected with more sensitivity.

In addition to the above configuration, the electric field detectionportion 10 is provided with a conductive case 15 surrounding theperiphery of the FET 11 in condition that the conductive case 15 iselectrically separated from the FET 11, and thereby detection other thanthe detection of the walking quasi-electrostatic field HSE of the usercan be avoided to the utmost extent.

Furthermore, in the electric field detection portion 10, as shown inFIG. 8 for example, the electrode surface 12 a of the detectionelectrode 12 faced with the user's epidermis OS is divided in multiplemicroelectrodes with almost the same shape and the same size, and an FETand an amplifier (not shown) are connected to each of the dividedmicroelectrodes in the same connection condition as the FET 11 and theamplifier 14 of the detection electrode 12 and in a different route fromthe route to the FET 11.

Thus, in the electric field detection portion 10 (FIG. 7), the strengthchange of the walking quasi-electrostatic field HSE formed on the user'sepidermis OS, which is caused by a walking motion of the user, is sentto a low-pass filter (hereinafter referred to as an LPF) 22 via eachmicroelectrode as an amplified walking electrification change signal S1,and the strength change is sent to a tissue information generationportion 21 via each microelectrode as local amplified walkingelectrification change signals A1 to An.

The walking motion described in this embodiment means a movement ofwalking on a flat passage surface without being especially conscious ofthe speed.

The sending portion 20 comprises the tissue information generationportion 21, the LPF 22, a waveform processing portion 23 and amodulation circuit 24. It inputs the amplified walking electrificationchange signal A1 to An from among the amplified walking electrificationchange signal S1 and the amplified walking electrification changesignals A1 to An supplied by the electric field detection portion 10 tothe tissue information generation portion 21, and inputs the amplifiedwalking electrification change signal S1 to the LPF 22.

As described above with reference to FIG. 5, the amplified walkingelectrification change signals A1 to An are potentials of the human bodydetected by respective microelectrodes as relative potentialdifferences, showing a potential difference pattern indicating thecharacteristics of the living tissue including the subepidermal tissueand veins below the detection electrode 12.

The tissue information generation portion 21 performs analog-digitalconversion processing on the amplified walking electrification changesignals A1 to A based thereon to digitalize them, generates thesubepidermal tissue pattern under the detection electrode 12 astwo-dimensionally represented tissue information D5 based on each of thedigitalized amplified walking electrification change data, and sends itto the modulation circuit 24.

The LPF 22 abstracts a component with a low frequency at 20 Hz or below,for example, from the amplified walking electrification change signal S1supplied by the amplifier 14 and sends it to the waveform processingportion 23 as a walking electrification change signal S2.

As shown in FIG. 9, the waveform processing portion 23 comprises an A/D(analog/digital) conversion portion 41, a peak detection portion 42, apeak prediction portion 43, a masking time determination portion 44 anda walking information generation portion 45. The waveform processingportion 23 digitalizes the walking electrification change signal S2supplied by the LPF 22 with the A/D conversion portion 41 and sendsresultant walking electrification change data D1 to the peak detectionportion 42 and the walking information generation portion 45.

As shown in FIG. 10 (A), the peak detection portion 42 monitors the bandof 8 Hz±2 Hz in the electrification change waveforms in the walkingelectrification change data D1 supplied by the A/D conversion portion 41and detects an 8 Hz peak Px which appears in this band.

When detecting the 8 Hz peak Px, the peak detection portion 42 generatesthe time when the 8 Hz peak Px has been detected (hereinafter referredto as the current time) t(n) based on the clock in the card device 3 ascurrent time data D2 and sends it to the peak prediction portion 43.

The peak prediction portion 43 holds the time (hereinafter the time iscalled as past time) t(n−1) of a past 8 Hz peak Px stored in an internalmemory (not shown), which had appeared immediately before the 8 Hz peakPx which appeared at the current time t(n), and predicts, based on thecurrent time t(n) and the past time t(n−1), the time (hereinafterreferred to as future time) t(n+1) of a future 8 Hz peak Px which willappear immediately after the 8 Hz peak Px which appeared at the currenttime by adding the difference between the current time t(n) and the pasttime t(n−1) to the current time t(n) as represented by the followingformula:t(n+1)=t(n)+(t(n)−t(n−1))  (15)

The peak prediction portion 43 generates the future time t(n+1) aspredicted time data D3 and sends the predicted time data D3 and thecurrent time data D2 to the masking time determination portion 44.

As shown in FIG. 10 (B), the masking time determination portion 44determines the time zone (hereinafter referred to as a masking timezone) MTZ to be modulated by the modulation circuit 24 (FIG. 7) on thesubsequent stage by calculating a start time ST(n) and a finish timeFT(n) of the masking time zone MTZ.

Specifically, the masking time determination portion 44 presets inadvance a period (hereinafter referred to as a predicted peak decreasingperiod) Δt1 which begins when the 8 Hz peak Px appears and ends when apredetermined amplitude level is reached, and calculates the start timeST(n) of the masking time zone MTZ in accordance with the followingformula:ST(n)=t(n)+Δt1  (16)

The masking time determination portion 44 also presets in advance aperiod (hereinafter referred to as a predicted peak increasing period)Δt2 which begins at a predetermined amplitude level and ends when the 8Hz peak Px appears, and calculates the finish time FT(n) of the maskingtime zone MTZ in accordance with the following formula:FT(n)=t(n+1)−Δt2  (17)

In this way, by removing the predicted peak decreasing period Δt1 andthe predicted peak increasing period Δt2 preset in advance from theinterval (hereinafter referred to as an 8 Hz peak interval) PS betweenan 8 Hz peak Px and the 8 Hz peak Px which appears immediately after the8 Hz peak Px), the masking time determination portion 44 determines themasking time zone MTZ, in which the 8 Hz peak Px is avoided, and sendsit to the modulation circuit 24 (FIG. 7) as masking time data D4.

The walking information generation portion 45 acquires the walkingelectrification change data D1 supplied by the A/D conversion portion41, for a predetermined time period, recognizes all the 8 Hz peaks Px(FIG. 10(A)) which appear in the electrification change waveform in thewalking electrification change data D1 corresponding to thepredetermined time period, and removes such 8 Hz peak intervals PS thatare beyond a predetermined allowable range in comparison withpeak-interval average-width information stored in advance in theinternal memory, from among the 8 Hz peak intervals PS of the recognized8 Hz peaks Px (FIG. 10(B)).

In this case, since the 8 Hz peak Px is set as an index, the walkinginformation generation portion 45 is able to accurately leave the 8 Hzpeak intervals PS corresponding to steady walking motion portions.

Then, the walking information generation portion 45 cut outs a portioncorresponding to the portion from the center position of the 8 Hz peakPx to the immediate position between the 8 Hz peak Px and the 8 Hz peakPx immediately before the 8 Hz peak Px plus the portion from the centerposition of the 8 Hz peak Px to the immediate position between the 8 Hzpeak Px and the 8 Hz peak Px immediately after the 8 Hz peak Px, as aone-step waveform TH, as shown in FIG. 11.

In this case, since the 8 Hz peak Px is also set as an index, thewalking information generation portion 45 is able to accurately cut outthe portion as a one-step waveform TH corresponding to an actual onestep in a walking motion.

The walking information generation portion 45 divides the one-stepwaveform TH into, for example, twenty-one subdivided sections CSU1 toCSU21 with almost equal intervals, in the time axis direction;integrates and normalizes each of the amplitude values (valuesindicating electrification change strength) for each of the dividedsubdivision sections CSU1 to CSU21; generates resultant twenty-oneintegral values as walking information D7 indicating the characteristics(walking pattern) of each portion in the one-step waveform TH; and sendsit to the modulation circuit 24 (FIG. 7).

The modulation circuit 24 performs data modulation processing on ID(IDentifier) information D6 stored in a memory (not shown) in the carddevice 3 in advance when the card device 3 was manufactured, forexample, then performs data modulation processing on the tissueinformation D5 supplied by the tissue information generation portion 21,and finally performs data modulation processing on the walkinginformation D7 supplied by the walking information generation portion45. The modulation circuit 24 is able to change the order of data onwhich a data demodulation process should be performed, as required,based on a predetermined setting operation.

Specifically, the modulation circuit 24 performs data modulationprocessing on the ID information D6 (the tissue information D5 or thewalking information D7) with a predetermined modulation method togenerate a modulated signal HS with a high frequency, and applies themodulated signal HS to an electrification induction electrode 31 onlyduring the masking time zone MTZ in the masking time data D4 supplied bythe masking time determination portion 44.

The electrification induction electrode 31 oscillates according to thefrequency of the modulated signal HS supplied by the modulation circuit24 only during the masking time zone MTZ, and a quasi-electrostaticfield (modulated signal HS) is generated from the electrificationinduction electrode 31 according to the oscillation.

Such quasi-electrostatic field (modulated signal HS) causes the user tobe electrified only during the masking time zone MTZ according to theoscillation (modulated signal HS) of the electrification inductionelectrode 31 and thereby act as an antenna, and as shown in FIG. 10(C),a quasi-electrostatic field according to the oscillation (hereinafterreferred to as an information-transmission quasi-electrostatic field)DSE (FIG. 6) isotropically spreads around the surface of the user.

As described above, in the sending portion 20, by changing theelectrification condition of a user, the user is caused to act as anantenna, and as the result, an information-transmissionquasi-electrostatic field DSE is formed on which the ID information D6(the tissue information D5 or the walking information D7) issuperimposed.

In this case, in the sending portion 20, the user is electrified duringthe masking time zone MTZ (FIG. 10), in which the 8 Hz peak Px whichappears with the highest strength in the strength change in the walkingquasi-electrostatic field HSE is avoided, so that the ID information D6superimposed on the information-transmission quasi-electrostatic fieldDSE can be prevented from being destroyed by the 8 Hz peak Px.

If the relative permittivity of the air is represented by 1, thewavelength in the air is represented by λ, the maximum distance forcommunication between the card device 3 and the authentication device 2is represented by r, and the frequency of the modulated signal HS to besupplied to the electrification induction electrode 31 is represented byf, then the sending portion 20 is able to propagate, from theelectrification induction electrode 31 to the user, aquasi-electrostatic field oscillating in accordance with the frequency fwhich satisfies the following formula: $\begin{matrix}{f < \frac{c}{2{\pi \cdot r}}} & (18)\end{matrix}$which is obtained by substituting the formula (10) into the formula (12)described above and rearranging the resultant formula.

Accordingly, when performing near field communication by causing a userwho is passing through the entrance/exit passage portion 4 to act as anantenna, the sending portion 20 is able to form the communication spaceas space (substantially closed space) where a non-propagatinginformation-transmission quasi-electrostatic field DSE (FIG. 6) isalways dominant, as described above with reference to FIGS. 3 and 4, andas a result, the communication output can be weakened to the extent thatthe communication contents are not propagated outside the communicationspace, and therefore, confidentiality of the communication contents canbe secured more sufficiently.

The sending portion 20 is actually adapted to perform a sending processat the tissue information generation portion 21, the LPF 22, thewaveform processing portion 23 and the modulation circuit 24 assoftware, in accordance with a predetermined sending program, under thecontrol of a control portion not shown. The procedure for the sendingprocess will be now described using the flowchart below.

As shown in FIG. 12, the sending portion 20 proceeds from the start stepof a routine RT1 to the next step SP1, where it abstracts alow-frequency component of an amplified walking electrification changesignal S1 supplied by the electric field detection portion 10 togenerate a walking electrification change signal S2 and proceeds to thenext step SP2.

At step SP2, the sending portion 20 performs analog-digital conversionbased on the walking electrification change signal S2 to generatewalking electrification change data D1, and proceeds to a masking timedetermination processing routine SRT1.

As shown in FIG. 13, at step SP11, the sending portion 20 detects the 8Hz peak Px (FIG. 10(A)) based on the walking electrification change dataD1 generated at step SP2 (FIG. 12), and after recognizing the currenttime t(n) thereof, it proceeds to the next step SP12.

At step SP12, the sending portion 20 predicts the future time t(n+1) ofan 8 Hz peak Px which will be detected next to the 8 Hz peak Px detectedat step SP11 from the above formula (15), and proceeds to the next stepSP13.

At step SP13, the sending portion 20 determines the masking time zoneMTZ by calculating the start time ST(n) and the finish time FT(n) fromthe above formulas (16) and (17), based on the current time t(n)recognized at step SP11 and the future time t(n+1) predicted at stepSP12, and proceeds to the next walking information generation processingroutine SRT2 (FIG. 12).

As shown in FIG. 14, at step SP21, the sending portion 20 acquires thewalking electrification change data D1 generated at step SP2 (FIG. 12),corresponding to a predetermined time period, and then proceeds to stepSP22.

At step SP22, the sending portion 20 recognizes all the 8 Hz peaks Px(FIG. 10(A)) appearing in the walking electrification change data D1corresponding to a predetermined time period, acquired at step SP21, andthen proceeds to the next step SP23.

At step SP23, the sending portion 20 removes 8 Hz peak intervals PS thatcorrespond to movements other than steady walking motions, such aswalking motions performed when starting or finishing walking andmovements performed when stopping walking, from among the 8 Hz peakintervals PS (FIG. 10(B)) of the 8 Hz peaks Px recognized at step SP22,and then proceeds to the next step SP24.

At step SP24, the sending portion 20 cut outs a one-step waveform TH(FIG. 11) from the waveform in the walking electrification change dataD1 corresponding to a steady walking motion portion, and then proceedsto the next step SP25.

At step SP25, the sending portion 20 divides the one-step waveform THcut out at step SP24 into, for example, twenty-one subdivided sectionsCSU1 to CSU21; integrates and normalizes the amplitude values of thesubdivided sections CSU1 to CSU21 to generate walking information D7;and then proceeds to the next step SP3 (FIG. 12).

At step SP3, the sending portion 20 generates tissue information D5based on the amplified walking electrification change signals A1 to Ansupplied by the electric field detection portion 10, and then proceedsto the next step SP4.

At step SP4, the sending portion 20 performs data modulation processingon the ID information D6 supplied from the memory in the card device 3,the tissue information D5 generated at step SP3, or the walkinginformation D7 generated by the walking information generationprocessing routine SRT2 to generate a modulated signal HS, and thenproceeds to the next step SP5.

At step SP5, by applying the modulated signal HS generated at step SP4to the electrification induction electrode 31 to change theelectrification condition of the user during the masking time zone MTZdetermined by the masking time determination processing routine SRT1,the sending portion 20 modulates the walking quasi-electrostatic fieldHSE (FIG. 6) formed in the neighborhood of the user (FIG. 10(C)), andthen proceeds to the next step SP6.

In this case, the information-transmission quasi-electrostatic field DSE(FIG. 6) formed isotropically around the surface of the user is acquiredby the authentication device 2.

At step SP6, the sending portion 20 determines whether or not the datamodulation processing has been completed at step SP4. If it has not beencompleted yet, the sending portion 20 returns to step SP4 and performsthe data modulation processing again. On the contrary, if it has beencompleted, the sending portion 20 proceeds to the next step SP7 and endsthe sending process.

As described above, in the sending portion 20, by changing theelectrification condition of a user only during the masking time zoneMTZ (FIG. 10), in which the 8 Hz peak Px appears with the higheststrength in the strength change in the walking quasi-electrostatic fieldHSE is avoided, it is possible to cause the user to act as an antennaand form an information-transmission quasi-electrostatic field DSE (FIG.6) in the neighborhood of the user while avoiding the modulated signalHS is destroyed by the 8 Hz peak Px.

(2-3) Configuration of an Authentication Device

As shown in FIG. 15, the authentication device 2 comprises an electricfield detection portion 50 and an authentication processing portion 60.

The electric field detection portion 50 is provided on the internalsurface of the entrance/exit passage portion 4 at the entrance side, forexample, and comprises a detection electrode 52 without suchmicroelectrodes as described above with reference to FIG. 8 (that is,with the electrode surface not divided) instead of the detectionelectrode 12 in the electric field detection portion 10 (FIG. 7) of thecard device 3. Except for this, the configuration is the same as that ofthe electric field detection portion 10.

The authentication processing portion 60 comprises an LPF 22 similar tothat in the sending portion 20 (FIG. 7) of the card device 3, a waveformprocessing portion 61 with the same configuration as that of thewaveform processing portion 23 without the walking informationgeneration portion 45 (FIG. 9), and an authentication portion 62.

The authentication device 2 detects strength change in aninformation-transmission quasi-electrostatic field DSE (a walkingquasi-electrostatic field HSE) formed in the neighborhood of a usercoming near to the entrance/exit passage portion 4 to pass through it,via the electric field detection portion 50 and the amplifier 14sequentially as an amplified walking electrification change signal S11,almost at the same time as the card device 3 does; abstracts only alow-frequency component with the LPF 22; and sends it as anelectrification change signal S12 to the waveform processing portion 61and the authentication portion 62.

In this case, the waveform processing portion 61 performs each of theprocessings similar to those described above with reference to FIG. 13based on the electrification change signal S12 at the same time theprocesses are performed by the card device 3, and after that, itdetermines the masking time zone MTZ corresponding to the same time zoneof the card device 3, and then sends it to the authentication portion 62as masking time data D14.

The authentication portion 62 performs a predetermined authenticationprocess based on the masking time data D14 supplied by the waveformprocessing portion 61 and the electrification change signal S12 suppliedby the LPF 22, using an ID list prestored in an internal memory (notshown), registrant tissue information and registrant walking informationregistered in the internal memory in advance by a predeterminedregistration process.

The registration process is performed during a walking motion of theuser with a detection electrode (not shown) of a predeterminedregistration device attached to the same portion of the user's arm wherethe detection electrode 12 (FIG. 7) of a card device 3 supplied to theuser is to be attached, in contact therewith, when a card device 3 issupplied to a user, for example.

In this case, the registration device generates registrant tissueinformation that two-dimensionally shows the tissue pattern under theepidermis under the detection electrode and registers it in the internalmemory of the authentication device 2, similarly to the card device 3.Furthermore, as shown in FIG. 16, for example, the registration devicedivides each of one-step waveforms TH for five steps into twenty onesubdivided sections CSU1 to CSU21 (FIG. 11), and then registers a set oftwenty one integral values for the subdivided sections CSU1 to CSU21(hereinafter referred to as a group of registered parameters) obtainedas a result of integration and normalization, in the internal memory ofthe authentication device 2 as registrant walking information indicatingwalking characteristics of the registrant, similarly to the card device3.

As the authentication process, the authentication portion 62 firstperforms demodulation processing on the electrification change signalS12 supplied by LPF 22 in accordance with a predetermined demodulationmethod only during the masking time zone MTZ in the masking time dataD14, and abstracts the ID information D6, the tissue information D5 orthe walking information D7 superimposed on the electrification changesignal S12 (the information-transmission quasi-electrostatic field DSE).

The authentication portion 62 then checks the ID list stored in theinternal memory against the ID information D6 as the first stage. Andthen, only when there is information corresponding to the ID informationD6 in the ID list, it checks the registrant tissue information stored inthe internal memory against the tissue information D5 as the secondstage. And then, only when there is registrant tissue informationcorresponding to the tissue information D5, it checks the registrantwalking information stored in the internal memory against the walkinginformation D7 as the third stage. And then, only when there isregistrant walking information corresponding to the walking informationD7, it opens the exit door 5 of the entrance/exit passage portion 4(FIG. 7).

An authentication processing portion 60 is actually adapted to performthe authentication process by the LPF 22, the waveform processingportion 61 and the authentication portion 62 as software, in accordancewith a predetermined sending program, under the control of a controlportion not shown. The procedure for the authentication process will benow described using the flowchart below.

As shown in FIG. 17, the authentication processing portion 60 proceedsfrom the start step of the routine RT2 to the next step SP31, andgenerates electrification change data by performing each of the sameprocessings as performed at the steps SP1 and SP2 (FIG. 12) by the carddevice 3 described above, on the amplified walking electrificationchange signal S11 detected and supplied by the electric field detectionportion 50 at the same time when the card device 3 does, and thenproceeds to the next masking time determination processing routineSRT11.

In the masking time determination processing routine SRT11, theauthentication processing portion 60 determines a masking time zone MTZby performing each of the same processings of the masking timeprocessing routine SRT1 (FIG. 13) for the card device 3, on theelectrification change data generated at step SP31, and then proceeds tothe next step SP32.

At step SP32, the authentication processing portion 60, by performingdata demodulation processing on the electrification change datagenerated at step SP31 during the masking time zone MTZ determined bythe masking time determination processing routine SRT11, abstracts theID information D6, the tissue information D5 or the walking informationD7 superimposed on the electrification change data, and then proceeds tothe next step SP33.

At step SP33, the authentication processing portion 60 checks the IDinformation D6 abstracted at step SP32 against the ID list prestored inthe internal memory, and determines whether or not there is informationcorresponding to the ID information D6 in the ID list.

If there is no such information, this indicates that the device is notthe card device 3 supplied by the company but a fake device. In thiscase, the authentication processing portion 60 proceeds to the next stepSP36 and ends the authentication process.

On the contrary, if such information exists, this indicates that thedevice is the card device 3 supplied by the company. In this case, theauthentication processing portion 60 proceeds to the next step SP34.

At step SP34, the authentication processing portion 60 checks the tissueinformation D5 abstracted at step SP32 against the registrant tissueinformation registered in the internal memory in advance to determinewither or not there is registrant tissue information corresponding tothe tissue information D5.

If there is no registrant tissue information, this indicates that theuser having the card device 3 is not a person related to the company. Inthis case, the authentication processing portion 60 proceeds to the nextstep SP36 and ends the authentication process.

On the contrary, if such registrant tissue information exists, thisindicates there is a high possibility that the user having the carddevice 3 is a person related to the company. In this case, theauthentication processing portion 60 proceeds to the next walkingchecking processing routine SRT13.

At step SP41 in FIG. 18, the authentication processing portion 60determines, for the set of integral values obtained from a one-stepwaveform detected at step SP32, the Mahalanobis' distance from thecenter of distribution of registered parameters which are alreadyregistered with the authentication processing portion. The Mahalanobis'distance is determined for all the registrants.

Practically, the shorter the Mahalanobis' distance is, the higherregistrant identification rate the authentication processing portion 60calculates, and the longer the Mahalanobis' distance is, the lowerregistrant identification rate it calculates.

At step SP43, the authentication processing portion 60 determineswhether or not any of the multiple registrant identification ratescalculated at step SP42 is equal to or above 90%. If less than 90%, thisindicates that the correspondence rate of the one step of the userrelative to the registrant's step registered in the internal memory islow, that is, the user is not the registrant himself. In this case, theauthentication processing portion 60 identifies that the user is not theregistrant, and it proceeds to the next step SP36 and ends theauthentication process.

On the contrary, if 90% or greater, this indicates that the user is theregistrant himself. In this case, the authentication processing portion60 recognizes that the user is a person related to the company andproceeds to the step SP35 (FIG. 17).

At step SP35, the authentication processing portion 60 opens the exitdoor 5 (FIG. 6) of the entrance/exit passage portion 4, and after that,it proceeds to the next step SP36 and ends the authentication process.

As described above, the authentication processing portion 60 not onlydetermines the identity of the card device 3 based on the ID informationD6 but also determines the identity of the user based on the tissueinformation D5 (living tissue pattern) and the walking information D7(walking pattern), and thereby it can securely identify the relationbetween the card device 3 and the user without performing specialprocessing such as encryption processing on the tissue information D5 toD7 on the side of the card device 3. Thus, the authentication processingportion 60 can even prevent a third person who has stolen a card device3 from passing through the entrance/exit passage portion 4 instead ofthe user (a person related to a company).

(2-4) Auxiliary Means in Near Field Communication

In addition to the above configuration, as shown in FIG. 20, theauthentication system 1 is provided with a floor surface (hereinafterreferred to as a route floor surface) Y1 of the entrance/exit passageportion 4 in such a condition that it is not grounded to the ground(hereinafter referred to as a building floor surface) Y2 but isseparated from the building floor surface Y2 by predetermined space dx(a gap).

In this case, the electrostatic capacity between the feet of the userand the building floor surface Y2 can be reduced to be less than theelectrostatic capacity between the user and the side-surface electrode 7by the amount corresponding to the space dx between the route floorsurface Y1 and the building floor surface Y2, and thereby leakage of theinformation-transmission quasi-electrostatic field DSE (walkingquasi-electrostatic field HSE) from the feet to the building floorsurface Y2 can be prevented.

In addition to this, it is also possible to prevent noises (hereinafterreferred to as environmental noises) KN caused by inconsistency of thebuilding floor surface Y2, such as electrical discharge noises caused byelectrically unstable condition due to a gap between joint surfaces ofsteel material in the building floor surface Y2 or rust of the steelmaterial, from being induced from the route floor surface Y1 to theuser.

Thus, in the communication system, it is possible to form, in a morestable condition, the equipotential surface of theinformation-transmission quasi-electrostatic field DSE (walkingquasi-electrostatic field HSE) which is formed substantiallyisotropically from around the surface of the user when the user iselectrified and the electrification change momentarily conducts over theperiphery of the surface of the user, and therefore it is possible tostable near field communication.

This will be visually apparent from comparison of FIG. 21 showing theequipotential surface of a quasi-electrostatic field when a human bodyfunctions as an ideal dipole antenna and FIG. 22 showing the results ofexperiments according to the present embodiment.

Furthermore, as shown in FIG. 23, the authentication device 2 of theauthentication system 1 is adapted to prevent leakage of a signal on theroute from the detection electrode 52 to the authentication processingportion 60 via the FET 11 and the amplifier 14. Specifically, first, aconductive case 15 is electrically separated from the FET 11; andsecond, only the authentication processing portion 60 is connected tothe ground on the receiving route.

Third, as means for preventing such leakage, the authentication device 2is adapted to reduce the electrostatic capacity SC1 between the FET 11and the ground in comparison with the electrostatic capacity SC2 on theroute from the FET 11 to the ground via the authentication processingportion 60, for example, by increasing the interval (height) between theFET 11 and the ground.

Thus, the authentication device 2 can efficiently induce theinformation-transmission quasi-electrostatic field DSE (walkingquasi-electrostatic field HSE) detected by the detection electrode 52 tothe authentication processing portion 60 via the FET 11, and therebyreceive the information-transmission quasi-electrostatic field DSEformed around the user with high sensitivity.

(2-5) Operation and Effect

In the communication system 1 with the above configuration, the tissueinformation D5 and the walking information D7 as living organismidentifying information are detected from the detection electrode 52 viathe FET 11, based on the walking quasi-electrostatic field HSE formed inthe neighborhood of the user, during a walking motion of the user whichis essentially required for the user to pass through the entrance/exitpassage portion 4 (FIG. 6)

Accordingly, in the authentication system 1, it is possible to obtaininformation with high identifiability specific to the user withoutcontrolling the movement of the user and without performing specialprocessing such as encryption.

Furthermore, since the tissue information D5 and the walking informationD7 are obtained from the same the detection electrode 52, theauthentication system 1 can be miniaturized. Thereby, uncomfortablefeeling of the user can be reduced by reduction of the area to be incontact with the human body.

In this situation, in the card device 3 in the authentication system 1,a quasi-electrostatic field modulated according to the field informationD5 and the walking information D7 (ID information D6) specific to theuser is generated to electrify the user, and the information is sent viathe information-transmission quasi-electrostatic field DSE withconfidentiality which is isotropically formed in the neighborhood of theuser.

In this case, in the authentication system 1, the nature of aquasi-electrostatic field and the nature of a user (human body) areutilized, and by the card device 3 and the authentication device 2detecting the 8 Hz peak Px common to human bodies from a movementpattern specific to the user and performing the same processing at thesame time, the masking time zone MTZ is determined.

As described above, in the authentication system 1, during a walkingmotion of the user which is essentially required for the user to pass anentrance/exit passage portion 4 (FIG. 7), a quasi-electrostatic fieldgenerated by electrification or walking of a user is used not onlysynchronize the sending and receiving sides but also acquire specifictissue information D5 and walking information D7. Furthermore, thetissue information D5 and the walking information D7 are sent andreceived with the quasi-electrostatic field formed around the user usedas an antenna. Thereby, the efficiency of communication can beconsiderably enhanced.

The authentication system 1 not only determines the identity of the carddevice 3 but also determines the identity of the tissue information D5(living tissue pattern) and the walking information D7 (walking pattern)specific to a user, and thereby even the relation between the carddevice 3 and the user can be securely identified without providingspecial processing such as encryption processing on the tissueinformation D5 to D7 on side of the card device 3.

According to the configuration described above, a quasi-electrostaticfield is used not only to synchronize the sending and receiving sidesbut also to acquire the tissue information D5 and the walkinginformation D7. Furthermore, the tissue information D5 and the walkinginformation D7 are sent and received using the quasi-electrostatic fieldgenerated around the user as an antenna, and thereby, sending andreceiving can be realized via the quasi-electrostatic field, without anydirectional restrictions in the neighborhood of the user, withconfidentially secured, and without forcing the user to perform apredetermined movement, and even the relation between the device and thehuman body can be identified based on information specific to the humanbody. Thus, the degree of freedom in communication using aquasi-electrostatic field can be enhanced.

(3) Other Embodiments

In the embodiment described above, description has been made on the casewhere the tissue information generation portion 21 for generating tissueinformation D5 based on amplified walking electrification change signalsA1 to An supplied via the detection electrode 12 of the electric fielddetection portion 10 or the walking information generation portion 45for generating walking information D7 based on an amplified walkingelectrification change signal S1 supplied by the detection electrode 12is applied as living organism information generation means forgenerating living organism information specific to a human body. Thepresent invention, however, is not limited thereto, and other variousliving information generation means for generating living organisminformation on various other living organisms such as fingerprints andcells can be applied.

In the embodiment described above, description has been made on the casewhere the 8 Hz peak Px is detected by the walking information generationportion 45 as walking information generation means, from the strengthdisplacement of the walking quasi-electrostatic field HSE formed arounda human body in response to a walking motion of the human body. Thepresent invention, however, is not limited thereto, and the peak of theelectric field displacement may be detected which is generated aroundthe human body by various other bipedal motions such as brisk walking,up-and-down movement on stairs and stepping movement on the same place,that is, such movements that include a state in which the entire plantarsurface of one foot is in contact with the ground and the tiptoe of theother foot has just left the ground.

In this case, the amplitude peak in the walking waveform changesaccording to the speed of the movement performed from when the rightfoot (left foot) completely gets in contact with the ground until whenthe tiptoe of the right foot (left foot) has just left the ground.Therefore, by detecting the amplitude peak that appears at the frequencyband according to the movement speed from when the right foot (leftfoot) in a bipedal motion to be detected is completely in contact withthe ground until when the tiptoe of the right foot (left foot) has justleft the ground as an index instead of the 8 Hz peak, the effect similarto that of the embodiment described above can be obtained.

In this case, if the masking time determination portion 44 changes thepredicted peak decreasing period Δt1 and the predicted peak increasingperiod Δt2 based on the frequency band according to the movement speedfrom when the right foot (left foot) in a bipedal motion to be detectedis completely in contact with the ground until when the tiptoe of theright foot (left foot) has just left the ground, then near fieldcommunication can be performed in a more stable condition.

In the embodiment described above, description has been made on the casewhere the card device 3 as a sending device is positioned on apredetermined portion of a user's arm in contact therewith. The presentinvention, however, is not limited thereto, and the card device 3 may bepositioned on various other portions of the epidermis of the user incontact therewith. For example, it may be embedded in a stud earring.

Furthermore, in the embodiment described above, description has beenmade on the case where the card device 3 is formed in a card shape. Thepresent invention, however, is not limited thereto, and the card device3 may be formed in various other shapes. After all any shape may bepossible only if it is of a mobile type.

Furthermore, in the embodiment described above, description has beenmade on the case where the route floor surface Y1 is provided for theentrance/exit passage portion 4 in a condition that it is separated fromthe building floor surface Y2 (FIG. 20) by predetermined space dx. Thepresent invention, however, is not limited thereto, and a member with alow relative permittivity may be filled in the space dx.

In this case, if the relative permittivity of the member filled betweenthe route floor surface Y1 and the building floor surface Y2 isrepresented by E, the gap between the route floor surface Y1 and thebuilding floor surface the building floor surface Y2 is represented bydx, the permittivity of vacuum electric constant is represented by ε0,and the area of the user's soles is represented by S, then theelectrostatic capacity CY2 between the user's feet and the buildingfloor surface Y2 approximates the relation represented by the followingformula: $\begin{matrix}{{{CY}\quad 2} = {{ɛ_{0} \cdot ɛ}\frac{S}{dx}}} & (19)\end{matrix}$Therefore, if the distance dx between the gate floor surface Y1 and theground surface Y2 and the relative permittivity E of the member filledbetween the gate floor surface Y1 and the ground surface Y2 are selectedin consideration of the above relation, the electrostatic capacity CY2between the user's feet and the ground surface Y2 can be certainlyreduced to be less than the electrostatic capacity between the user andthe detection electrode 52. Thus, leakage of theinformation-transmission quasi-electrostatic field DSE (walkingquasi-electrostatic field HSE) from the user's feet to the groundsurface Y2 can be prevented more securely, and thereby near fieldcommunication can be stabilized more securely.

Furthermore, in the embodiment described above, description has beenmade on the case where the route floor surface Y1 is provided for theentrance/exit passage portion 4 in a condition that it is separated fromthe building floor surface Y2 (FIG. 20) by predetermined space dx, ascoupling preventing means for preventing a user and the ground frombeing electrically coupled with each other. The present invention,however, is not limited thereto, and there may be provided a noiseabsorption/grounding line 80 laid on the route floor surface Y1 andgrounded to the building floor surface Y2, as shown in FIG. 24.

In this case, it is possible to prevent such noises (hereinafterreferred to as environmental noises) KN as are caused by inconsistencyof the building floor surface Y2 from being induced from the route floorsurface Y1 to the user and thereby stabilize the near fieldcommunication, similarly to the embodiment described above. Furthermore,if not only the space dx but also the noise absorption/grounding line 80is provided between the route floor surface Y1 and the building floorsurface Y2, stabilization of the near field communication can beenhanced more.

Furthermore, in the embodiment described above, description has beenmade on the case where electrification change of a user (aninformation-transmission quasi-electrostatic field DSE or a walkingquasi-electrostatic field HSE) is detected by an FET 1 (FET connected tomicroelectrodes) as the amplified walking electrification change signalS1 (A1 to An). The present invention, however, is not limited thereto,and the change in the electrification condition of the user may bedetected by various other detection means such as aninduction-electrode-type field strength meter for measuring the voltageinduced by induction voltage, an induction-electrode-typemodulation-amplification-system field strength meter for AC converting adirect signal obtained by an induction electrode using a choppercircuit, oscillation capacity and the like, an electro-optic-effect-typefield strength meter for applying en electric field to material havingan electro-optic effect to measure change in the light propagationcharacteristics caused in the material, and, only for the card device 3,an electrometer, a shunt-resistor-type field strength meter, acurrent-collection-type field strength meter and the like.

Furthermore, in the embodiment described above, description has beenmade on the case where electrification induction means is realized bythe modulation circuit 24 and the electrification induction portion 30.The present invention, however, is not limited thereto, and theelectrification induction means may be realized by various otherconfigurations.

Furthermore, in the embodiment described above, description has beenmade on the case where demodulation means is realized by the LPF 22 andthe authentication portion 62. The present invention, however, is notlimited thereto, and the demodulation means may be realized by variousother configurations.

Furthermore, in the embodiment described above, description has beenmade on the case where a user is identified by the authenticationportion 62 as identification means based on tissue information D5 andwalking information D7 as living organism information. The presentinvention, however, is not limited thereto, and a user may be identifiedon one of the tissue information D5 and the walking information D7.Alternatively, a user may be identified by living organism informationsuch as fingerprints combined with and added to the tissue informationD5 and the walking information D7.

Furthermore, in the embodiment described above, description has beenmade on the case where near field communication is performed via oneuser between the card device 3 as a mobile-type sending device providedin the neighborhood of the user and the authentication device 2 as areceiving device provided on a predetermined control target. The presentinvention, however, is not limited thereto, and near field communicationmay be performed via multiple users. In this case, the same effect asthat of the embodiment described above can be obtained.

Furthermore, in the embodiment described above, description has beenmade on the case where the present invention is applied to anauthentication system 1 which opens an exit door 5 as necessary when auser enters or exits from an entrance/exit passage portion 4 as acommunication route. The present invention, however, is not limitedthereto and can be broadly applied to authentication systems for variousother purposes, such as a communication system with a communicationroute in the neighborhood of the desk, for opening the door of a desk asnecessary when a user comes near to the desk, a communication systemwith a communication route in the neighborhood of a personal computer,for powering on the personal computer when a user comes near to thepersonal computer, and a communication system using a conveyance passagefor conveying a predetermined identification target as a communicationroute, for switching conveyance passages as necessary when theidentification target is conveyed to a predetermined position, that is,to any authentication system that electrifies a human body according toliving organism information specific to the human body to cause thehuman body to act as an antenna, on the sending side, and acquiresidentification information from a quasi-electrostatic field formed inthe neighborhood of the human body to authenticate the human body, onthe receiving side.

In this case, in the present invention, the authentication device 2 as areceiving device can be broadly applied to various other devicesprovided on or in the neighborhood of a video tape recorder, atelevision set, electronics such as a mobile telephone or a personalcomputer, medical equipment, an automobile, a desk, and other controltargets to be controlled, for example. In this case, the same effect asthat of the embodiment described above can be obtained.

Furthermore, in the embodiment described above, description has beenmade on the case where each of the processings by a sending portion 20or an authentication processing portion 60 is realized by a program. Thepresent invention, however, is not limited thereto, and a part or all ofeach processing may be realized by hardware means, such as an integratedcircuit dedicated the processing.

Furthermore, in the embodiment described above, description has beenmade on the case where the sending process (FIG. 12) or theauthentication process (FIG. 17) described above are performed inaccordance with a program prestored in an internal memory. The presentinvention, however, is not limited thereto, and the sending process orthe authentication process may be performed by mounting a programstorage medium in which the program is stored into an informationprocessor.

In this case, the program storage medium to have the program forexecuting the sending process or the authentication process installedand make it executable may be realized not only by a package media suchas a flexible disk, a CD-ROM (Compact Disk-Read Only Memory), and a DVD(Digital Versatile Disc) but also by a semiconductor memory or amagnetic disk in which the program is temporarily or permanently stored.As means for storing an analysis program in such a program storagemedium, a wired or wires communication medium, such as a local areanetwork, the Internet, and digital satellite broadcasting, may beutilized, and the analysis program may be stored via variouscommunication interfaces such as a router and a modem.

As described above, according to the present invention, in anauthentication system comprising sending and receiving devices forsending and receiving information via a quasi-electrostatic field, thesending device detects living organism information specific to a humanbody and generates a quasi-electrostatic field modulated according tothe living organism information to electrify the human body. Meanwhile,the receiving device demodulates the living organism information basedon change in the electrification condition of the human body andidentifies the human body based on the living organism information.Thereby, sending and receiving of information can be realized withoutany directional restriction in the neighborhood of a user, withconfidentiality secured, and without forcing the user to perform apredetermined movement. Furthermore, even the relation between thedevice and the human body can be identified based on the informationspecific to the human body. Thus, the degree of freedom in communicationwith a quasi-electrostatic field can be enhanced.

INDUSTRIAL APPLICABILITY

The present invention is adapted to an authentication system forperforming authentication using living organism information specific toa human body, for example, in the case of opening a door provided for apredetermined entrance/exit passage when the human body enters or exitsfrom the entrance/exit passage, in the case of unlocking a drawerprovided for a desk as necessary when the human body comes near to thedesk, and the like.

1. An authentication system comprising a sending device and a receiving device for sending and receiving information via a quasi-electrostatic field, characterized in that: the sending device comprises: living organism information generation means for generating living organism information specific to a human body; and electrification induction means for electrifying the human body by generating a quasi-electrostatic field modulated according to the living organism information; and the receiving device comprises: demodulation means for demodulating the living organism information based on change in the electrification condition of the human body; and identification means for identifying the human body based on the living organism information.
 2. The authentication system according to claim 1, characterized in that: the living organism information generation means comprises: a detection electrode contacted with the epidermis of the human body, for detecting potential change on the surface of the human body faced with the contacted surface; and tissue information generation means for generating tissue information indicating a tissue pattern under the portion of the epidermis of the human body faced with the contacted surface, as the living organism information based on the potential change detected by the detection electrode.
 3. The authentication system according to claim 2, characterized in that: the detection electrode comprises multiple microelectrodes electrically independent from one another; and the tissue information generation means generates the tissue information based on relative potential difference in the potential change detected by each of the microelectrodes.
 4. The authentication system according to claim 1, characterized in that: the living organism information generation means comprises: a detection electrode contacted with the epidermis of the human body, for detecting potential change on the surface of the human body faced with the contacted surface in response to a bipedal walking motion of the human body; and walking information generation means for generating walking information indicating a walking pattern of the human body, based on the potential change detected by the detection electrode.
 5. The authentication system according to claim 4, characterized in that: the walking information generation means generates the walking information with the amplitude peak that appears at a particular frequency band in the potential change as an index.
 6. The authentication system according to claim 1, characterized in that: the living organism information generation means comprises: a detection electrode contacted with the epidermis of the human body, for detecting potential change on the surface of the human body faced with the contacted surface in response to a bipedal walking motion of the human body; walking information generation means for generating walking information indicating a walking pattern the human body, based on the potential change detected by the detection electrode; and tissue information generation means for generating tissue information indicating a tissue pattern under the portion of the epidermis of the human body faced with the contacted surface, as the living organism information based on the potential change detected by the detection electrode.
 7. An authentication method for sending and receiving information via quasi-electrostatic field, characterized in comprising: on the sending side, a living organism information generation step of generating living organism information specific to a human body; and an electrification induction step of electrifying the human body by generating a quasi-electrostatic field modulated according to the living organism information; and on the receiving side, a demodulation step of demodulating the living organism information based on change in the electrification condition of the human body; and an identification step of identifying the human body based on the living organism information.
 8. A sending device for sending information via a quasi-electrostatic field, characterized in comprising: living organism information generation means for generating living organism information specific to a human body; and electrification induction means for electrifying the human body by generating a quasi-electrostatic field modulated according to the living organism information.
 9. The sending device according to claim 8, characterized in that: the living organism information generation means comprises: a detection electrode contacted with the epidermis of the human body, for detecting potential change on the surface of the human body faced with the contacted surface; and tissue information generation means for generating tissue information indicating a tissue pattern under the portion of the epidermis of the human body faced with the contacted surface, as the living organism information based on the potential change detected by the detection electrode.
 10. The sending device according to claim 8, characterized in that: the living organism information generation means comprises: a detection electrode contacted with the epidermis of the human body, for detecting potential change on the surface of the human body faced with the contacted surface in response to a bipedal walking motion of the human body; and walking information generation means for generating walking information indicating a walking pattern of the human body, based on the potential change detected by the detection electrode.
 11. A receiving device for receiving information via a quasi-electrostatic field, characterized in comprising: demodulation means for, based on change in the electrification condition of a human body electrified by a quasi-electrostatic field modulated according to living information specific to the human body, demodulating the living organism information; and identification means for identifying the human body based on the living organism information. 